This section is intended to provide information relevant to understanding various technologies described herein. As the section's title implies, this is a discussion of related art that should in no way imply that it is prior art. Generally, related art may or may not be considered prior art. It should therefore be understood that any statement in this section should be read in this light, and not as any admission of prior art.
Integrated circuits include circuitry to perform monitoring functions to assist with detecting whether a power supply has reached safe levels. Sometimes, integrated circuits are subject to current surges, and protection may be achieved with a type of circuit known as a power-on-reset (POR) detector.
FIG. 1 shows an example of a POR circuit. In this circuit, one or more diode drops are taken from a voltage supply VDD to charge an internal node N via a resistor-capacitor (RC) input circuit, where Rbig and Cbig are large. The diode D1 is used to ensure that the voltage supply VDD has reached at least 1-diode drop above ground (GND or VSS) before a reset signal is disabled. Unfortunately, with this type of circuit, the reset time constant can change significantly due to a strong dependence of diode voltage on temperature. For instance, compared to room temperature, the reset time can increase by 20× at cold temperature, while decreasing by 5× at hot temperature.